1. Field of the Invention
The present invention relates to an image detector for bank notes which is used when discriminating between bank notes.
2. Description of Related Art
Technology relating to image detectors for bank notes used for example when discriminating the authenticity, denomination and state of wear of bank notes, includes technology in which a light emitting unit arranged on one side of a bank note transportation path irradiates light onto a bank note, and the light transmitted through the bank note is detected by a light receiving unit arranged on the other side of the bank note transportation path, and technology in which light is irradiated onto a bank note from a light emitting section arranged on one side of a transportation path of a light emitting and receiving unit, and the reflected light is detected by a light receiving section of the same light emitting and receiving unit (see Patent document 1, for example). Furthermore, technology relating to image sensor modules used in such image detectors for bank notes has also been disclosed (see Patent document 2, for example).
Patent document 1: Japanese Unexamined Patent Application, First Publication No. Hei 2001-357429
Patent document 2: Japanese Patent No. 3099077
In order to improve the accuracy of discrimination when discriminating the authenticity, denomination and state of wear and the like of bank notes, one method is to discriminate based on the image of one side of the bank note, from either the front or back direction, the image of the reverse side of the bank note, and a front and back transmission image of the bank note, and discriminate based on these images collectively. However, when performing the discrimination in this manner, if the image detector for bank notes disclosed in patent document 1 is used, a first light emitting and receiving unit having a first image detection sensor and a first light emitting device is required for detecting the image on one side in the front and back direction of the bank note, from either the front or back direction, a second light emitting and receiving unit having a second image detection sensor and a second light emitting device is required for detecting the image of the reverse side in the front and back direction of the bank note, and a light emitting unit having a third light emitting device, and a light receiving unit having a third image detection sensor are required for detecting the front and back transmission image of the bank note. Since three image detection sensors are required for the respective light receptions, there is a problem in that cost is increased.